This invention relates generally to the field of medical devices and methods of treatment of spondylolisthesis, and more particularly to the field of such devices and methods for manipulation of adjacent vertebrae or of the lower vertebrae and the sacrum (which in humans is formed of fused vertebrae), whereby the adjacent vertebrae or the vertebrae and sacrum are properly aligned and positioned such that fixation structures can be utilized to secure the adjacent vertebrae or the vertebrae and sacrum in the proper relation. Even more particularly, the invention relates to a mechanical apparatus or jack which can be temporarily attached to spinal implants permanently affixed to both the vertebrae and the sacrum, whereby the surgeon performs the spondylolisthesis reduction by manipulating the jack to properly position the vertebrae and sacrum and then securing the sacrum spinal implant to the vertebral, spinal implant in rigid manner.
The invention herein functions with and incorporates portions of the apparatus and method disclosed in my U.S. Pat. No. 6,017,343, issued Jan. 25, 2000, and entitled Apparatus, Method and System for the Treatment of Spinal Conditions and Fixation of Pelvis and Long Bones, the disclosure of which is herein incorporated by reference. The invention will also function with other types of spinal implants and mechanical fixation devices used to create a construct which will secure the adjacent pairs of vertebrae or the sacrum and vertebrae in a fixed, rigid relationship, such as plates or rods.
The lumbar vertebrae comprise the five vertebrae positioned below the dorsal vertebrae, and are customarily designated L1 through L5, with L1 being adjacent the lowermost or twelfth dorsal vertebra and L5 being adjacent the sacrum. The sacrum is a large, curved, triangular bone having a wide base which articulates from the L5 vertebra. The anterior surface of the sacrum is generally concave, curving in a pronounced manner from above downward and slightly from side to side. Spondylolisthesis is a condition where adjacent vertebrae, most usually the sacrum and the lower or lumbar vertebrae, are not properly aligned or connected, such that adjacent vertebrae are displaced or the lumbar vertebrae are displaced anteriorly from the upper base of the sacrum. For purposes of this disclosure, the apparatus and method shall be described primarily with reference to spondylolisthesis occurring between the L5 vertebra and the sacrum, but it is to be expressly understood that the apparatus and method are suitable for manipulation and treatment of any adjacent vertebrae. In a spondylolisthesis reduction, the surgeon properly repositions the vertebrae and sacrum, and then permanently joins the vertebrae and sacrum using mechanical fixation structures. The reduction may require manipulation of the vertebrae and the sacrum in one or more directions, i.e., translation in the anterior/ventral or posterior/dorsal direction, compression or distraction in the longitudinal direction of the vertebral axis, and rotation about the vertebral axis, as well as pivotal flexion of the sacrum in the ventral direction or pivotal extension of the sacrum in the dorsal direction.
In my U.S. Pat. No. 6,017,343, spinal implants comprising linking members are disclosed which comprise a central portion joining two end portions, the end portions being apertured to receive a pedicle bolt whereby the link members can be permanently affixed to a vertebra or other bone. The end portions of adjacent link members are aligned to receive a single pedicle bolt and a lock nut, and in this manner pairs of link members can be connected to form a rigid linking structure, where the link members can be affixed to adjacent vertebrae, bones or bone segments in order to create a rigid connecting structure which secures the vertebrae, bones or segments in fixed manner.
It is an object of this invention to provide an apparatus, a system and a methodology for the manipulation and fixation of adjacent vertebrae or the lumbar vertebrae and the sacrum for spondylolisthesis reduction, whereby a mechanical manipulator device or jack is provided which allows the surgeon to properly position and secure the vertebrae and sacrum in a relatively quick and straightforward manner. It is a further object to provide such an apparatus and method which enables the surgeon to translate, compress, distract, rotate, flex or extend either or both the vertebrae and the sacrum as required, which is easily connected to and removed from spinal implant link members affixed to the vertebrae and the sacrum, and which functions to retain proper positioning of the vertebrae and sacrum as the surgeon connects the link members of the sacrum to the link members of the vertebrae. It is a further object to provide such an apparatus whose component parts are adjustable to accommodate variation in patient size and to present a variety of angular combinations as required for a particular reduction operation. These and other objects not expressly stated above will be readily apparent from examination of the disclosure to follow.
The invention comprises an apparatus and a method for performing spondylolisthesis reduction between adjacent vertebrae and more particularly between the lower vertebrae and the sacrum, where the method utilizes spinal implants, such as spinal link members comprising central portions bridging two apertured end portions, where the end portions of two such link members may be aligned to receive a pedicle bolt, a bolt which is driven into the vertebral body or the sacrum, or a joining bolt which is independent of the vertebral body or sacrum, such that the two link members can be secured to the vertebra or sacrum and to each other by lock nuts to form a rigid structure. The apparatus comprises a jack or manipulator device which is temporarily affixed to transversely mounted central portions of the spinal links, where the jack is constructed to provide leverage or fulcrum points such that the vertebrae or sacrum can be moved as required for proper realignment and to position adjacent link members for connection. The jack apparatus comprises a pair of outrigger members connected to a levering member, where the outrigger members and levering member are provided with plural apertures to receive pivot bolts, in order to allow for variation in the relative angular and linear dispositions of the members. The outrigger members and levering member are connected such that each is free to pivot, whereby the relative angle between the members may be altered by movement of the levering member, which is provided with at least one handle to be gripped by the surgeon. Optionally, an outrigger stabilizer member is also provided for attachment to the outrigger members in similar manner, such that the combination of the outrigger members, levering member and stabilizer member defines a four-sided polygon. The ends of the outrigger members are provided with connector means for temporarily securing the outriggers to the transverse portions of the linking members in a secure manner such that any manipulation of the outrigger members is transferred to the spinal link members and thus to the vertebra or sacrum to which they are affixed. The connector means preferably comprises a hook member which receives the transverse portion of the linking member and a threaded locking ring which can be translated against the transverse portion to secure it against the hook member of the outrigger member. The apparatus is also preferably provided with a position locking member which comprises an elongated body pivotally attached to the levering member, where the position locking member can be temporarily secured to one of the outrigger members to prevent relative movement between the outrigger members and the levering member in order to secure the apparatus in a particular angular configuration.
The preferred method comprises the steps of affixing spinal linking members to dorsal side of the base of the sacrum and to the dorsal side of at least the L5 vertebrae, or to any adjacent vertebrae. The spinal link members affixed to the sacrum preferably comprise one transversely mounted linking member whose central portion defines a transverse bridging member extending laterally across the sacrum and two longitudinally disposed linking members, where one end of each longitudinally disposed linking member is secured to an end of the transversely mounted linking member while the other end of each longitudinally disposed linking member remains free. A pair of longitudinally disposed linking members are each affixed to the L4 and L5 vertebra (an L4 to L5 fusion being representative of this technique), or to any two adjacent vertebrae that are slipped relative to each other, and a transversely mounted linking member is affixed across the L4 vertebra and connected to the longitudinally disposed linking members. Another pair of longitudinally disposed linking members are connected to the longitudinally disposed linking members on the L5 vertebra, with each having a free end. After proper reduction has been achieved, the free ends of the longitudinally disposed linking members on the sacrum and the L5 vertebra will be connected using a bolt and lock nut. To manipulate the vertebrae and sacrum as required, the outrigger members are joined to the transverse members of the spinal link members on the L4 vertebra and the sacrum, such that the outrigger members extend in the dorsal direction. The outrigger stabilizer member and levering member are then connected to the outrigger members to define a polygonal configuration, which may be a parallelogram, a trapezoid or other four-sided configurations. The surgeon then manipulates the vertebrae and sacrum as required by pulling on the levering handle and secures the apparatus against angular movement once proper positioning is achieved and the free ends of the longitudinally disposed linking members are aligned. The relative positions of the outrigger members and the levering member and stabilizer member may be changed during the course of the reduction as required to provide proper leveraging and positioning. The free ends of the linking members are then connected to form a rigid, interlocked construct which extends from the L4 vertebra through the L5 vertebra to the sacrum. The jack apparatus is then removed from the spinal link members.